World Clock
The time in every city you care about, day or night at a glance, and a full-screen clock.
Your time
World clock
Is my clock right?
Compares this device’s clock with the time reported by this website’s server, using six tiny requests timed to land on the server’s second boundaries. The requests ask for headers only and carry no cookies and nothing you have typed.
About the World Clock
A live clock for every city you work with or care about. Each card shows the local time with seconds, the date, the time-zone abbreviation and UTC offset, how far ahead or behind you it is, today’s sunrise and sunset, and the next daylight-saving change. Cards are shaded by the real position of the sun in that city — daylight, twilight or night — so you can see at a glance who is awake.
Switch between digital and analog faces and 12- or 24-hour time, open any clock in a big full-screen view (an online clock with seconds for a classroom, studio or exam hall), and use Is my clock right? to compare your device’s clock with this website’s server. Your city list is saved in your browser; the time-zone rules come from the IANA database built into your browser.
How to use it
- The big clock at the top shows your time, from your device’s clock and time zone. Press the full-screen button for a large clock with seconds; press it again or Esc to leave.
- Below it, each card is a city. Search Add a city or time zone by city, country or abbreviation (for example Toronto, Germany or PST) to add more, and use the × on a card to remove it (Undo brings it back).
- Press the expand button on a card to show that city in the big clock — handy for a full-screen clock of another time zone. The arrow button brings back your own time.
- Choose Digital or Analog, 12-hour or 24-hour, and whether to show seconds. Sort by time orders the cards from west to east, Copy times copies every clock as text and Copy link makes a link that opens the same cities.
- Press Check my clock to see whether your device’s clock is fast or slow, and by how much.
Examples
London 5:30 am (BST, 4h 30m behind) · New York 12:30 am (EDT, 9h 30m behind) · Tokyo 1:30 pm (JST, 3h 30m ahead) · Sydney 2:30 pm (AEST, 4h 30m ahead)
Sydney: clocks go forward on Sun 4 Oct · London: clocks go back on Sun 25 Oct · New York: clocks go back on Sun 1 Nov
After each change the gap between India and that city changes by an hour, because India keeps the same time all year.
Sunrise 6:15 am · sunset 6:05 pm (IST)
Common uses
- Keeping an eye on colleagues, clients or family in other countries before calling or messaging.
- Showing a large clock with seconds on a TV, projector or spare screen during an exam, live broadcast or event.
- Checking whether a computer, phone or tablet clock has drifted before timing something important.
How day, night and sunrise are worked out
Sunrise, sunset and civil twilight (the sun up to 6° below the horizon, when it is still fairly light) are calculated in your browser with the SunCalc library, which uses the formulas from Jean Meeus’ Astronomical Algorithms. Each listed city has its own coordinates, from the GeoNames geographical database (CC BY 4.0). For a time zone picked by name rather than by a listed city, the zone’s reference location from the IANA time zone database is used and the card says so. Times assume a flat horizon at sea level and are usually within a minute or two of published tables.
How “Is my clock right?” works
Web servers send their current time in the Date header of every response, to the whole second. The check sends six tiny requests to this website (requests for headers only, with no cookies and nothing you typed), notes your device’s clock before and after each one, and times the later requests so that they reach the server just as its clock ticks to a new second. Each reply narrows down the difference; the result is shown with its margin of error, which is usually a few hundredths of a second on a good connection.
The comparison is with this website’s server. Servers normally keep their clocks synchronised over the internet, but this is a practical check, not a certified time source. A slow or unstable connection makes the margin wider, and privacy settings that blur your browser’s clock make it less precise.
Daylight saving time
The clocks use the time-zone rules in your browser’s copy of the IANA time zone database, so a city switches between, say, GMT and BST on the right day without any change on this page. Each card shows the next change within a year — when clocks go forward or back, by how much and at what local time. Zones that never change, such as India Standard Time, show no line.
Limitations
- All clocks are driven by your device’s clock. If it is wrong, every card is wrong by the same amount — use Check my clock to find out.
- Time-zone rules are only as current as your browser; governments occasionally change them at short notice, so keep the browser updated.
- Sunrise and sunset ignore mountains, buildings and local refraction; the day/night shading is for orientation, not navigation.
- Full screen depends on the browser. Where a page cannot go full screen (for example on iPhone), the clock fills the browser window instead. Keeping the screen on uses the Screen Wake Lock API where the browser offers it.
Privacy
The clocks run entirely in your browser. Your list of cities and your display options are saved in this browser’s local storage and are not sent anywhere. The optional clock check sends header-only requests to this website, with no cookies and nothing you typed.
Frequently asked questions
What time is it now in another city?
Type the city, its country or a zone abbreviation into Add a city or time zone. The card shows the current time there with seconds, the date, whether it is ahead of or behind you, and its UTC offset.
How accurate is the clock check?
The result comes with a margin of error — usually a few hundredths of a second on a stable connection. A difference smaller than half a second, or within the margin, counts as right. Larger differences are reported as fast or slow; a difference of half an hour or more usually means a wrong time zone or date setting rather than a drifting clock.
How do I show a full-screen clock with seconds?
Press the full-screen button on the big clock. To show another city, press the expand button on its card first. Leave with Esc or the same button. Tick Keep the screen on to stop the screen from dimming, where your browser supports it.
Why is a card shaded blue or yellow?
The shading follows the sun in that city: plain for daylight, yellow during twilight around sunrise and sunset, and blue at night. It is worked out from the city’s coordinates, not from the hour on the clock.
Does the world clock handle daylight saving time?
Yes. Every clock follows the official rules for its zone, and each card shows the next date on which the clocks there go forward or back.